In the morning, put your cast iron Dutch oven in the oven. Add a pan of ice cubes or water, too. Heat to 500°F / 260°C.
When the oven is up to temp, remove the dough from the refrigerator. Remove the shower cap. If needed, gently pull the top of the edges away from the banneton. (I find it never gets floured enough right at that top rim.)
Put a piece of parchment over the dough. Then put a cutting board over that. Flip the whole thing and coax the dough out of the banneton.
Cut the parchment (if needed to fit better in your Dutch oven).
Dust the top of the loaf with flour and slash with a sharp knife or lame. If you're fancy, make a decoration. (Mine suck. I can do slashes. Period.)
Remove the Dutch oven from the oven and put the loaf in. Cover and return to the oven.
After about five minutes reduce the temperature of the oven to 425°F / 220°C.
Bake covered for 18-20 minutes.
Remove the lid of the Dutch oven, turn the Dutch oven around, and bake for another 20-25 minutes until internal temperature reaches 200°F / 93°C.
Turn the oven off.
Remove the loaf from the Dutch oven, discard the parchment, and return the loaf to the cooling oven with the door propped open a bit with a wooden spoon.
Remove from oven and cool completely on a wire rack.